Plasma pharmacokinetics and bioavailability of oxytetracycline were studied in Atlantic salmon (Salmo salar ) (weight 481.8 plus or minus 39.98 g, mean plus or minus 1 SD) held in reconstituted seawater at 15 degree C. Fish received a single dose of oxytetracycline (OTC) at a dose rate of 100 mg/kg body weight either intravascularly through an indwelling cannula placed in the dorsal aorta or per os via intragastric intubation. Blood samples were collected over an 8 day period beginning immediately prior to medication. Plasma samples were assayed for OTC content by a modification of the Association of Official Analytical Chemists (AOAC) microbiological assay for oxytetracycline in feeds. Oral bioavailability was determined to be 6.88% (95% confidence intervals of 1.9% and 24.9%) and the elimination of oxytetracycline (0-24 h post treatment) was best described by an open two-compartment model.